Ch 24 - Viruses and Prokaryotes 1-1

Ch 24 - Viruses and Prokaryotes 1-1 - Viruses and...

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Viruses and Prokaryotes (earliest life forms) Chapter 24 The Virus (Virion) A-cellular: cannot independently perform metabolic activities Sub-cellular particle: passes through filters that block prokaryotes Consists of DNA or RNA genome (ss/ds) surrounded by protein coat (capsid) Sometimes acquires an envelope What are they? Viruses may be bits of nucleic acid that originally “escaped” from animal, plant, or bacterial cells (the three domains) as mobile genetic elements: transposons (a DNA segment that can move across chromosomes and integrate) Plasmids (small circular ds DNA molecules that carry genes distinct from those in the main DNA of a cell) Fragments moved from cell to cell, across species, through damaged membranes genetic similarity between viruses and their host cells Or viruses may have evolved even earlier before the three domains diverged Mimiviruses: Evolved from a more complex ancestor; gradually lost some of the genes necessary for protein synthesis Became dependent upon a host (amoeba) for complete protein synthesis. Virus Structure Viral Reproductive Cycles Lytic cycle virus destroys host cell Virulent (cause disease) Self limiting Lysogenic cycle: temperate viruses
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Viral genome becomes integrated into host DNA (provirus, prophage) replicates along with host DNA Can revert to lytic cycle with stimulation (UV, X-rays) Bacteriophages (phages) exemplify the differences between a lytic cycle and a lysogenic viral cycle Phages are viruses that infect bacteria Can be used in Pharma to kill bacteria resistant to certain antibiotics Lytic Cycle Lysogenic Cycle Lysogenic conversion Corynebacterium diphtheriae : Toxin-producing strain contains phage coding for toxin, causing diphtheria Non-toxin producing strain does not Clostridium botulinum
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This note was uploaded on 02/11/2010 for the course BIO 01-119-10 taught by Professor D'arville during the Spring '09 term at Rutgers.

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Ch 24 - Viruses and Prokaryotes 1-1 - Viruses and...

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